Functional biodiversity and plasticity of methanogenic biomass from a full-scale mesophilic anaerobic digester treating nitrogen-rich agricultural wastes

Abstract

The effect of ammonia on methanogenic biomass from a full-scale agricultural digester treating nitrogen-rich materials was characterized in batch activity assays subjected to increasing concentrations of total ammonia N. Acetotrophic and methanogenic profiles displayed prolonged lag phases and reduced specific activity rates at 6.0 gN-TAN L, though identical methane yields were ultimately reached. These results agreed with the expression levels of selected genes from bacteria and methanogenic archaea (qPCR of 16S rRNA and mrcA cDNA transcripts). Compound-specific isotope analysis of biogas indicated that ammonia exposure was associated to a transition in methanogenic activity from acetotrophy at 1.0 gN-TAN L to intermediate and complete hydrogenotrophy at 3.5 and 6.0 gN-TAN L. Such pattern matched the results of 16S-Illumina sequencing of genes and transcripts in that predominant methanogens shifted, along with increasing ammonia, from the obligate acetotroph Methanosaeta to the hydrogenotrophic Methanoculleus and the poorly understood methylotrophic Methanomassiliicoccus. The underlying bacterial community structure remained rather stable but, at 6.0 gN-TAN L, the expression level increased considerably for a number of ribotypes that are related to potentially syntrophic genera (e.g. Clostridium, Bellilinea, Longilinea, and Bacteroides). The predominance of hydrogenotrophy at high ammonia levels clearly points to the occurrence of the syntrophic acetate oxidation (SAO), but known SAO bacteria were only found in very low numbers. The potential role of the identified bacterial and archaeal taxa with a view on SAO and on stability of the anaerobic digestion process under ammonia stress has been discussed.

The Effect of Operating Strategies on the Anaerobic Digestion of Gentamicin Mycelial Residues: Insights into the Enhancement of Methane Production and Attenuation of Gentamicin Resistance

“…In addition to TAN and FA, some common metabolites were also determined to describe the changes of AD performance under different operating strategies. High TAN has been believed to trigger the accumulation of VFAs due to blocked acetate metabolism . As a result, VFAs in the effluent of MMAD were found to be the highest among all the reactors (Figure a).…”

Energy Availability Determines Strategy of Microbial Amino Acid Synthesis in Volatile Fatty Acid–Fed Anaerobic Methanogenic Chemostats

“…In AMCs, syntrophic fatty acid–oxidizing bacteria and methanogens cooperate to perform the conversion of fatty acids to methane, acting as the core functional groups ( Nobu et al, 2015 ). However, it was confusing why the community members that are not involved in the core metabolism were present in the AMCs and how they contribute to the development and function of the AMCs ( Ruiz-Sánchez et al, 2019 ; Wang P. et al, 2020 ). Our results suggest that those noncore functional bacteria are crucial for producing the costly AAs (tryptophan, tyrosine, histidine, and phenylalanine) that support the survival of the core functional groups.…”

Treatment of the Supernatant of Anaerobically Digested Organic Fraction of Municipal Solid Waste in a Demo-Scale Mesophilic External Anaerobic Membrane Bioreactor

“…Ammonia nitrogen in the reactors was in the range of 2.4-4.3 g NH 4 + -N•L −1 , and the estimated free ammonia values were 452-811 NH 3 -N•L −1 , which have been reported as inhibitory in anaerobic digestion processes (Chen et al, 2008;Yenigün and Demirel, 2013), and Pedizzi et al (2018) obtained better anaerobic digestion performance decreasing the initial ammonia concentration with the same samples used in this experiment. This inhibition can be overcome at high SRT, favoring the hydrogenotrophic methanogenesis pathway (Ruiz-Sánchez et al, 2019).…”

“…The VFA behavior can be understood considering the high ammonia contents of the influent, of the same order of magnitude when bioreactor was operated as CSTR, even higher, but with a lower inhibitory effect when AnMBR is operated at high SRT (low OLR). Ammonia inhibition has been observed to decrease when operating at high sludge retention time (Bhattacharya and Parkin, 1989) or at HRT higher than 40 d in CSTR (Ruiz-Sánchez et al, 2019), since the acetoclastic methanogenic pathway shifts to the hydrogenotrophic pathway by the action of syntrophic acetate-oxidizing bacteria (SAOB), which are more tolerant to high ammonia levels than acetoclastic methanogens (Wang et al, 2015). Since SAOB doubling time is much higher than acetoclastic methanogens, high SRTs are needed to avoid SAOB washout (Westerholm et al, 2016), and Tian et al (2018) obtained a successful acclimation at high ammonia nitrogen concentration with an HRT of 23 days.…”